Pope Francis marks 12 years as head of the Catholic Church on Thursday, seemingly out of danger after a month in hospital but with his health casting a shadow over his future.

The 88-year-old was, for a time, critically ill as he battled pneumonia in both lungs at Rome's Gemelli hospital, where he was admitted on Feb. 14.

The Argentine's situation has markedly improved since then, with the Vatican confirming his condition as stable on Wednesday evening, and talk is now turning to when he might go home.

But his hospitalization, the longest and most fraught of his papacy, has raised serious doubts about his ability to lead the world's nearly 1.4 billion Catholics.

Slowing down

Francis had before now refused to make any concessions to his age or increasingly fragile health, which saw him begin using a wheelchair three years ago.

He maintained a packed daily schedule interspersed with frequent overseas trips, notably a 12-day tour of the Asia-Pacific region in September, when he presided over huge open-air masses.

But experts say his recovery could take weeks given his age and recurring health issues, not helped by having part of one lung removed as a young man.

"The rest of his pontificate remains a question mark for the moment, including for Francis himself," said Father Michel Kubler, a Vatican expert and former editor in chief of the French religious newspaper La Croix.

"He doesn't know what his life will be like once he returns to the Vatican and so, no doubt, reserves the option of resigning if he can no longer cope," he told AFP.

Francis has always left the door open to resigning were his health to deteriorate, following the example of Benedict XVI, who in 2013 became the first pope since the Middle Ages to voluntarily step down.

But the Jesuit has distanced himself from the idea more recently, insisting the job is for life.

While in hospital, Francis has delegated masses to senior cardinals but has kept working on and off, including signing decrees and receiving close colleagues.

But he has missed a month of events for the 2025 Jubilee, a holy year organized by the pope that is predicted to draw an additional 30 million pilgrims to Rome and the Vatican.

And it is hard to imagine he will be well enough to lead a full program of events for Easter, the holiest period in the Christian calendar that is less than six weeks away.

Many believe that Francis, who has not been seen in public since he was hospitalized, has to change course.

"This is the end of the pontificate as we have known it, until now," Kubler said.

Unfinished reforms

Francis struck a sharp contrast to his cerebral predecessor when he took office, eschewing the trappings of office and reaching out to the most disadvantaged in society with a message that the Church was for everyone.

A former archbishop of Buenos Aires more at home with his flock than the cardinals of the Roman Curia, Francis introduced sweeping reforms across the Vatican and beyond.

Some of the changes, from reorganizing the Vatican's finances to increasing the role of women and opening the Church to divorced and LGBTQ members, have been laid down in official texts.

But a wide-ranging discussion on the future of the Church, known as a Synod, is not yet finished.

And there are many who would happily see his work undone.

Traditionalists have strongly resisted his approach, and an outcry in Africa caused the Vatican to clarify its authorization of non-liturgical blessings for same-sex couples in 2023.

"Whether we like him or not, he has shifted the dial, but many things are still pending," a Vatican source said.